Installa il pacchetto firmware-ralink.
Prima però aggiungi ai repository main i contrib e non-free.
codice:deb http://ftp.it.debian.org/debian/ jessie main contrib non-free deb-src http://ftp.it.debian.org/debian/ jessie main contrib non-free deb http://security.debian.org/ jessie/updates main contrib non-free deb-src http://security.debian.org/ jessie/updates main contrib non-free